The Hindu Business Line : `Tune in to CDMA'

`With base stations in a particular area creating interference among themselves, the capacity of a base station becomes less. I cannot reuse spectrum but need additional spectrum.'

Dr Eshwar Pitampalli

AS the debate over the efficiency of different telecommunication technologies rages in the industry, eWorld thought an academic who is also a technologist could give us an objective viewpoint.

Here we give you Lucent Technologies' Chief Technical Officer, India, Dr Eshwar Pitampalli's views on the spectrum and other raging issues. Dr Pitampalli is a Bell Labs Fellow. Prior to this, he worked in the Wireless Standards Development Department of Mobility Solutions at Lucent Technologies where he was responsible for the CDMA2000 radio access network standards.

Excerpts from the conversation:

When it migrated to the new licence, CDMA was said to be five times more efficient than GSM. That was one of the reasons why they started off with a handicap.

If someone is less efficient and you want to give that person more, then it's no longer an ideal race. There is discrimination.

In allocating spectrum, would being neutral to technology be the right thing to do now or should you change the rules as you go along?

Even though the race has started, going forward, every time a player becomes eligible for more spectrum, allot spectrum per additional subscriber added to all concerned.

If CDMA was spectrally efficient, then the same handicap should prevail at every stage. Can you change it now?

The GSM side claimed it only to get more spectrum. The Government was so naïve that they did not know how exactly to use a national scarce resource. But, the GSM people have gone on record to prove that they are as spectrally efficient as CDMA. Why is the Government closing its eyes? Since both CDMA and GSM are radio frequency signals, then both technologies would be spectrally equal.

To assume that GSM is spectrally less efficient than CDMA is wrong. I do not think the Government should continue to practise the wrong form of implementation of their spectrum allocation policy.

Then have they made a mistake at the starting line?

Really. They made a big blunder. Not a small mistake.

The claims are that GSM base stations can use base station efficiency... . That is multiple base stations can together be more efficient than just a single one, whereas CDMA operators can show more efficiency in a single base station.

Since there is no additional spectrum available currently, both technologies would need more and more base stations in a given area as subscribers increase in that area. CDMA is based on`interference limited' or unwanted signals that come into that particular base station. The CDMA capacity is controlled by interference created in the base station. With more base stations in a particular area creating interference amongst themselves, the capacity of a base station becomes consistently less. If one base station in a sq.km supported 100 subscribers, four base stations in the same area cannot support 400. So, I cannot reuse spectrum but would need additional spectrum.

Based on TRAI's recommendations, CDMA should be allocated spectrum immediately while GSM could get it in a staggered fashion till December 2006.The GSM players are contesting this.

The question that CDMA operators are asking is: Whatever you do, be technology-neutral and allocate equal spectrum to both players.

The handicap arose because CDMA came in at a later date. CDMA players were to be fixed-line players who later became mobile players. And allocation of spectrum was done on that basis. Are the rules changing midway?

(There is) absolutely no point saying that rules are changing midway, because, to begin with, CDMA operators were disadvantaged. It is CDMA that defined competition here and has reached 15-million subscriber density, (making services affordable). Given this, the Government should, in fact, be encouraging CDMA operators by giving them more spectrum.

In 3G, the migration path is easier for CDMA, technology-wise. So when spectrum allocation happens, it would help CDMA players move into 3G faster than GSM. Your views?

Nobody is stopping GSM folks from migrating to CDMA 3G and vice-versa. The question is if it is easy for CDMA people to go onto 3G compared to GSM, why do you want to penalise the CDMA folks? They have just chosen the right technology.

If a new player wants to get into 3G directly, how should the allocation be done? As Telecom Regulatory Authority of India (TRAI) rules stand, 2 GHz should be given equally to all players. Then there is nothing left for new players.

I think the Government might want to take a re-look at that. Competition does generate more services and advantages to basic subscribers.

Also, 3G is being brought in to take high-paying voice subscribers into the higher band of spectrum and keep the lower end in 2G technology. Isn't that a dilution of what 3G is capable of on the data front?

CDMA technology currently, within 1.25 Mhz, can support voice capacity of 26.4 erlangs of voice traffic. Now, if you used the same 1.25 Mhz bandwidth for 1X EVDO (or 3G services), which is data optimised, then if that service is only focused on voice, it would support 35 erlangs of voice. What this means is, with 35erlangs you can allocate 25 erlangs for voice, I have 10 additional erlangs for 3G data applications. So, spectrum is not wasted but only better utilised.

There seems to be congestion in the networks. That is the reason why we are opening up new spectrum that seems to be mainly for subscribers now on 2G.

There is an assumption that there is no band available in 1900. That is wrong. In fact, CDMA operators have been asking for USPCS band, or the US personal communications services band. They are not asking for the entire 60 Mhz band but only for 2 Mhz of this. The reason why 2100 is not good for India for 3G is that it is not used anywhere on this planet. Let us assume 3G is going to provide voice too, 2100 is a new spectrum for which there are no vendors supplying infrastructure or handsets at this point, anywhere in the world. Since there are no economies of scale, the cost would be prohibitive. The cost of the handset will not be less than $150! When the common man here is looking at a $25-mobile or below, how will the $150-mobile be attractive?

TRAI says that our Defence is not willing to vacate the 1900 band and that is why 2Ghz comes into the picture.

Did anyone question TRAI saying `Open up your frequency allocation. We would like to see what exactly is being used by Defence?'

My belief is that one camp is making sure that it provides all the information (from its point of view) so that the other camp doesn't get the frequency it should get. The Government should open this up and make it public.

Were these opinions not aired at the open house consultations that TRAI did at different points?

Maybe it wasn't really open house. Maybe it was an open house to closed members.

With GSM in 1800 Mhz and 1900 Mhz being opened up for CDMA, could there be a lot of interference given that two concurrent bands are opened up for 3G. Is that a reason why probably GSM operators are opposing the move to open up 1900 Mhz?

If someone wants to oppose something, then someone is going to find a reason to oppose. A drunkard needs an excuse to drink. If you watch movies of Amitabh Bachchan, in several of which he acts a drunkard, that's the theme of his dialogue. So, interference is only an excuse on the part of GSM to oppose the opening up of 1900.

There is always the facility of filters. Even with CDMA and GSM, without a filter, I am going to interfere with the next band. So you need to use the appropriate filter to avoid interference. It's all there. It's not a new concept.

bharatk@thehindu.co.in

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